handle rc versions of gradle in version compare (#141612)

- handle number format exceptions and strip rc information from version compare
- add test that handles rc format

part 2/n https://github.com/flutter/flutter/issues/138523

Helpfully pointed out by [asaarnak](https://github.com/asaarnak) https://github.com/flutter/flutter/pull/139325#issuecomment-1892554584

dev/devicelab/bin/tasks/module_test.dart

@@ -450,5 +450,6 @@ Future<void> main() async {
   await task(combine(<TaskFunction>[
     // ignore: avoid_redundant_argument_values
     ModuleTest('module-gradle-7.6', gradleVersion: '7.6.3').call,
+    ModuleTest('module-gradle-7.6', gradleVersion: '7.6-rc-2').call,
   ]));
 }

packages/flutter_tools/gradle/src/main/groovy/flutter.groovy

@@ -1423,6 +1423,7 @@ class FlutterPlugin implements Plugin<Project> {
 
     // compareTo implementation of version strings in the format of ints and periods
     // Requires non null objects.
+    // Will not crash on RC candidate strings but considers all RC candidates the same version.
     static int compareVersionStrings(String firstString, String secondString) {
         List firstVersion = firstString.tokenize(".")
         List secondVersion = secondString.tokenize(".")
@@ -1430,12 +1431,32 @@ class FlutterPlugin implements Plugin<Project> {
         def commonIndices = Math.min(firstVersion.size(), secondVersion.size())
 
         for (int i = 0; i < commonIndices; i++) {
-            def firstAtIndex = firstVersion[i].toInteger()
+            String firstAtIndex = firstVersion[i]
-            def secondAtIndex = secondVersion[i].toInteger()
+            String secondAtIndex = secondVersion[i]
+            int firstInt = 0;
+            int secondInt = 0
+            try {
+                if (firstAtIndex.contains("-")) {
+                    // Strip any chars after "-". For example "8.6-rc-2"
+                    firstAtIndex = firstAtIndex.substring(0, firstAtIndex.indexOf('-'))
+                }
+                firstInt = firstAtIndex.toInteger()
+            } catch (NumberFormatException nfe) {
+                println(nfe)
+            }
+            try {
+                if (firstAtIndex.contains("-")) {
+                    // Strip any chars after "-". For example "8.6-rc-2"
+                    secondAtIndex = secondAtIndex.substring(0, secondAtIndex.indexOf('-'))
+                }
+                secondInt = secondAtIndex.toInteger()
+            } catch (NumberFormatException nfe) {
+                println(nfe)
+            }
 
-            if (firstAtIndex != secondAtIndex) {
+            if (firstInt != secondInt) {
                 // <=> in groovy delegates to compareTo
-                return firstAtIndex <=> secondAtIndex
+                return firstInt <=> secondInt
             }
         }